Variable speed tumbling dryer



United States Patent Ofiice 3,365,810 Patented Jan. 30, 1968 The present invention relates to a method of dying clothes in a clothes-drying appliance.

As clothes are tumbled in conventional dryers, there is a substantial tendency toward intertwining, tangling, and balling with various types of loads. With such conventional appliances, it is possible for some garments to become wrapped within a larger garment, causing ineflicient drying performance due to the non-uniform moisture distribution at the conclusion of the drying cycle.

One of the objects of the present invention is to provide an improved method for the drying of clothes involving the use of at least two tumbling speeds.

Another object of the invention is to provide an improved drying method in which the clothes being tumbled in the dryer are periodically tumbled at a higher speed than exists in the normal drying operation to thereby break up any tendency for the clothes being dried to ballup.

A further object of the invention is to provide an improved method for drying clothes involving the use of differing tumbling speeds at various portions in the drying cycle while heated air is being passed through the drying drum.

The method of the present invention provides several advantages. For one, the total drying time is reduced because there is better contact of the hot air with the fabrics. For another, there is more uniform and consistent drying of the clothes tumbled in this manner, so that the range of water retention in the clothes at the end of the drying cycle does not vary as widely as it does with the conventional single speed tumbling operation.

In accordance with the present invention, the fabrics are dried in a rotatable drum at a first clothes tumbling speed for a predetermined period of time. Subsequently, the drum is rotated while the drying airstream is still passing into it at a tumbling speed which is faster than the initial tumbling speed. The second tumbling interval of the higher tumbling speed is not greater than the initial tumbling interval, and is usually significantly less.

Both of the tumbling operations are carried out at rotational speeds which are sufficient to carrying the clothes to the point where they exceed the angle of repose and drop to the base of the drum, to be again transported by the rotation of the drum to a position where they again tumble through the heated air to the bottom of the drum. At no tirne during the entire drying cycle is the rotation of the drum sufliciently high to cause the fabrics to continually bear against the periphery of the drum by virtue of centrifugal force and be carried around the drum during its rotation. In other words, at no time during the alternate sequence of tumbling operations does the centrifugal force on the clothes exceed the factor of 1 G.

A further description of the present invention will be made in conjunction with the attached sheet of drawings which illustrates one type of dryer which can be used to practice the method of the present invention.

In the drawings:

FIGURE 1 is a view partly in elevation and partly in cross-section of a dryer assembly embodying the improvements of the present invention; and

FIGURE 2 is a cross-sectional view taken substantially along the line HII of FIGURE 1.

As shown in the drawings:

In FIGURE 1 reference numeral indicates generally a dryer having an outer casing 11 provided with an access door 12 at its forward end. Mounted within the easing 11 is a drum 13 in which the articles to be dried are tumbled. The drum 13 has a stub shaft 14 which mounts in a bearing generally indicated at reference numeral 16 and fixedly secured to the casing 11.

A flat drive belt 17 is strained about the periphery of the drum 13 and is driven by a drive pulley 18 driven by a motor 19. An adjustable tensioning roller 21 bears against the belt 17 to provide the belt with the proper tension at diiferent operating speeds, as will be apparent from a succeeding portion of this description. The tensioning roller 21 is mounted for rotation on a bell crank lever 22 which is pivoted from the cabinet at a pivot 23. The opposite end of thebell crank lever 22 is connected to a helical spring 24 which is fixed to the bottom of the cabinet.

A strip 26 wound in helical form about the drum 13 engages a toothed wheel 27 behind a tooth 27:: as illustrated in FIGURE 1. As the drum 13 makes one revolution, it rotates the Wheel 27 one tooth clockwise due to the lead angle of the strip 26. Upon the completion of the single revolution, the strip then is in position to engage the wheel 27 behind the tooth 27b, so that each revolution of the drum 13 provides an incremental rotation of the toothed wheel 27.

The wheel 27 carries a lug 28 which is arranged to engage a gear 29 which carries a cam 31 mounted for rotation on a shaft 32. Eventually, the lug 28 rotates the gear 29 sufficiently so that the lobe of the cam 31 displaces a roller 35 carried by a pivoted parallelogram linkage generally identified at reference numeral 33. The resulting pivotal movement of the linkage 33 causes an arm 34 carried by the linkage to move to the right as viewed in FIGURE 1. The arm 34 carries a pair of rollers 36 and 37 disposed on opposite sides of the belt 17. The movement of the arm 34 thereby shifts the belt 17 from engagement with a reduced diameter portion 38 of the pulley 18 to an enlarged shoulder portion 39 of the pulley. Since the enlarged portion 39 is of a greater diameter than the end portion 38, and the speed of the motor is constant, the belt 17 is driven faster during this interval than when the belt 17 is engaged with the reduced diameter end portion 38. Tension on the belt 17 is provided by the pivoting of the lever 22, and consequent movement of the roller 21 against the action of the spring 24 to accommodate the shifting of the belt 17 The drum 13 is rotated at this increased speed until such time as the lobe of the cam 31 moves away from the roller 35. A spring 41 pulls the parallelogram linkage 33 back to its original position, so that the belt 17 is shifted back to the position shown in FIGURE 1 Where it engages the smaller diameter end 38 of the motor pulley. This cycle of alternating tumbling speeds is repeated during succeeding intervals by the movement of the wheel 27 and the cam 31 after a predetermined number of revolutions of the drum 13. The length of running time at either tumbling speed can be changed by adding more teeth to the wheel 27 or by adding more lobes ot the cam 31, as required. It is, of course, possible to provide more than two tumbling speeds, if desired, by adding a number of different diameters on the motor pulley.

During both the tumbling intervals, heated air is intro duced through the drum. The air is received from outside the cabinet through an inlet 42, passes over a heating coil 43 or similar heating device, and is exhausted into the interior of the drum 13 through an outlet 44, as indicated by the arrows appearing in FIGURE 2. A fan 46 draws the heated drying air through the drum and exhausts it through a suitable vent 47.

Best results are obtained in the newly described process by correlating the drum speeds during each tumbling interval, and the duration of each tumbling interval. For a val, during which drying efiiciency is greatest, is of longer duration than the second drying interval, this second interval being only long enough to accomplish breaking up any balling Which might occur during the first drying interval. The rotational speed used to achieve the results will, of course, vary with the drum diameter and the appropriate speeds for any given drum diameter can be calculated from the well known relationship that centrifugal force is directly proportional to the square of the peripheral velocity and inversely proportional to the radius. In all cases, the speed should be such as to provide less than a 1 G centrifugal force on the clothes so that true tumbling action is achieved during all portions of the cycle. The difference in tumbling pattern which results between the first and second tumbling speeds tends to break up any balling which may occur during the first drying period.

It should be evident that various modifications can be made to the described embodiments without departing from the scope of the present invention.

The embodiments of the invention in Which an exclusive'property or privilege is claimed are defined as follows:

1. The method of drying clothes in a clothes dryer having'a rotatable drum comprising:

(a) rotating said drum in the presence of a drying airstream at a first clothes tumbling speed for a first perdetermined period,

(b) rotating said drum in the presence of a drying airstream at a second clothes tumbling speed faster than said first speed for a scond predetermined period,

(c) alternately repeating the steps set forth in (a) and (b) throughout a clothes drying cycle.

2. The method of drying clothes set forth in claim 1 wherein the ratio of said first predetermined period to said second predetermined period is greater than one.

3. The method of drying clothes set forth in claim 1 wherein both said first and second clothes tumbling speeds create less than a 1 G centrifugal force on said clothes.

4. The method of drying clothes in a clothes dryer having a rotatable drum comprising:

(a) rotating said drum in the presence of a drying airstream at a first clothes tumbling speed for a first period of approximately two to six minutes,

(b) rotating said drum in the presence of a drying airstream at a second clothes tumbling speed faster than said first speed for a second period of approximately one-half to two and one-half minutes, the ratio of said first period to said second period being greater than one, and

(c) alternately repeating the steps set forth in (a) and (b) throughout a ClO'thes drying cycle.

5. The method of drying clothes set forth in claim 4 wherein both said first and second clothes tumbling speeds create less than 1 G centrifugal force on said clothes.

6. The method of drying clothes in a clothes dryer having a rotatable drum comprising:

(a) rotating said drum during a first period in the presence of a drying airstream at a first clothes tumbling speed for obtaining maximum drying efficiency,

(b) rotating said drum during a second period in the presence of a drying airstream at a second speed for breaking up the tumbling pattern of said clothes established during said first period, and,

(c) alternately repeating the steps set forth in (a) and (b) throughout a clothes drying cycle.

7. The method of drying clothes set forth in claim 6 wherein said second speed is faster than said first speed.

8. The method of drying clothes set forth in claim 6 wherein the ratio of said first period to said second period is greater than one.

9. The method of drying clothes set forth in claim 8 wherein said first speed is greater than said second speed.

10. The method of drying clothes in a clothes dryer having a rotatable drum which comprises:

(a) rotating said drum at a first tumbling speed for a predetermined drying interval while passing heated drying air through said drum,

(b) increasing the speed of rotation of said drum at the conclusion of said predetermined drying interval to a second tumbling speed while still passing said drying air through said drum for a second predetermined drying interval of lesser duration than the aforementioned predetermined drying interval, and

(c) repeating steps (a) and (b) in sequence during the drying operation.

References Cited UNITED STATES PATENTS 3,186,104 6/1965 Stilwell 34-45 3,197,884- 8/1965 Smith 3445 3,286,359 11/1966 Orr et a1. 3412 KENNETH W. SPRAGUE, Primary Examiner. 

1. THE METHOD OF DRYING CLOTHES IN A CLOTHES DRYER HAVING A ROTATABLE DRUM COMPRISING: (A) ROTATING SAID DRUM IN THE PRESENCE OF A DRYING AIRSTREAM AT A FIRST CLOTHES TUMBLING SPEED FOR A FIRST PREDETERMINED PERIOD, (B) ROTATING SAID DRUM IN THE PRESENCE OF A DRYING AIRSTREAM AT A SECOND CLOTHES TUMBLING SPEED FASTER THAN SAID FIRST SPEED FOR A SECOND PREDETERMINED PERIOD, (C) ALTERNATELY REPEATING THE STEPS SET FORTH IN (A) AND (B) THROUGHOUT A CLOTHES DRYING CYCLE. 